The aim of this study was to identify risk factors for acute diarrhoea (AD) during the summer in France. A matched case-control study was conducted at a national level among patients of 500 general practitioners (GPs). From July to September 1996, 468 case-control pairs were included. Cases were more likely than controls (i) to live away from their main residence (OR 3.0; 95% CI 1.6-5.7), (ii) to have returned from a country at high risk of AD (OR 4.6; CI 0.9-23.1), and (iii) to have been in contact with a case of AD (OR 2.0; CI 1.3-3.1). A significantly decreased risk of AD was found for consumption of well-cooked chicken (OR 0.5; CI 0.3-0.8) and raw or undercooked home-made egg-containing products (OR 0.6; CI 0.4-0.8). These findings suggest that travel to high-risk areas, or travel within France, and being in contact with a case of AD, are risk factors for the occurrence of AD in summer in France.